In
machining, 2.5D refers to a surface which is a projection of a plane into 3rd dimension – although the object is 3-dimensional, there are no overhanging elements possible. Objects of this type are often represented as a contour map that gives the height (''i.e.'', thickness or depth) of the object at each point.
2.5D objects are often greatly preferred for machining, as it is easy to generate
G-code
G-code (also RS-274) is the most widely used computer numerical control (CNC) programming language. It is used mainly in computer-aided manufacturing to control automated machine tools, and has many variants.
G-code instructions are provided to ...
for them in an efficient, often close to optimal fashion, while optimal
cutting tool
In the context of machining, a cutting tool or cutter is typically a hardened metal tool that is used to cut, shape, and remove material from a workpiece by means of machining tools as well as abrasive tools by way of shear deformation. The major ...
paths for true 3-dimensional objects can be
NP-complete
In computational complexity theory, a problem is NP-complete when:
# it is a problem for which the correctness of each solution can be verified quickly (namely, in polynomial time) and a brute-force search algorithm can find a solution by trying ...
(nondeterministic polynomial time complete), although many algorithms exist.
2.5D objects can be machined on a 3-axis
milling machine
Milling is the process of machining using rotary cutters to remove material by advancing a cutter into a workpiece. This may be done by varying direction on one or several axes, cutter head speed, and pressure. Milling covers a wide variety of d ...
, and do not require any of the features of a higher-axis machine to produce.
A 2.5D machine, also called a two-and-a-half-axis mill, possesses the capability to translate in all three axes but can perform the cutting operation only in two of the three axes at a time due to hardware or software limitations, or a machine that has a solenoid instead of a true, linear Z axis. A typical example involves an XY table that positions for each hole center, where the spindle (Z-axis) then completes a fixed cycle for drilling by plunging and retracting axially. The code for a 2.5D machining is significantly less than 3D contour machining, and the software and hardware requirements are (traditionally) less expensive. Drilling and tapping centers are inexpensive, limited-duty machining centers that began as a 2.5-axis market category, although many late-model ones are 3-axis because the software and hardware costs have dropped with advancing technology.
A 2.5D image is a simplified three-dimensional (x, y, z) surface representation that contains at most one depth (z) value for every point in the (x, y) plane.
References
{{Metalworking navbox, machopen
Computer-aided engineering